From 1964-1967, the NFL cards were printed by the Philadelphia Gum Company. Topps only printed AFL cards during those 4 seasons. Beginning in 1968, the Topps set included NFL and AFL players, so this is the last AFL-only set.
Here are the 2 checklists.
Unlike the baseball sets, the Topps (and Philly Gum) football sets were organized by team prior to 1968.
I only bought one pack of AFL cards in 1967, which included these:
Each pack included an insert card, showing a pennant. At first glance it looks like a legitimate sports team, but the fine print says otherwise. The Air Force card came in my first pack.
I got this one years later, but it's my only other one, so here it is.
The AFL card backs look like this:
I have most of the Chiefs, Dolphins, and Chargers cards, but only a few of the others.